The present invention relates to patterned abrading articles and, in particular, it relates to patterned abrading articles comprising a substrate having raised portions with an abrasive material deposited on the raised portions.
Coated abrasive articles generally contain an abrasive material, typically in the form of abrasive grains, bonded to a backing by means of one or more adhesive layers. Abrasive articles can be used for sanding, grinding or polishing various surfaces of, for example, steel and other metals, wood, wood-like laminates, plastic, fiberglass, leather or ceramics.
Many abrasive articles are used as discs, in grinding assemblies. Typical abrasive sanding or grinding assemblies include a support pad made from a resilient and reinforced material such as rubber or plastic, an abrasive disc, which is typically frictionally mounted on the backup pad and a rotatable shaft and cap for mounting the abrasive disc and backup pad by pressure applied to the disc upon screwing the cap into the shaft so that the disc is squeezed against the backup pad. In use, the shaft of the assembly is rotated and the abrasive coated surface of the disc presses against a workpiece.
In general, there are two methods of manufacturing coated abrasive discs. The first method is to manufacture the abrasive disc from a coated abrasive web produced from known techniques, e.g., coating at least one binder and the abrasive grains on a cloth, vulcanized fiber, paper, or similar backing. The cured abrasive web is then converted, via die cutting, into substantially circular discs.
The second type of abrasive disc manufacture is to commence with a backing already in the desired final form, i.e., circular with desired diameter and optional central hole or holes. This disc backing is then coated with a first binder, commonly referred to as make coating. Abrasive grains are then embedded into the make coating and the make coating is exposed to conditions sufficient to solidify the make coating to a degree to adhere the abrasive grains to the backing. A second binder is then coated over the abrasive grains and then solidified. Another method is to coat the backing with a slurry of resin and mineral. Typical backings used include vulcanized rubber, vulcanized fiber, and metal (aluminum or steel).
Both methods of manufacture set forth above are widely used for the production of abrasive discs, although problems are inherent of each. The discs punched from a web usually have a fairly thin backing, typically about 100 to 2500 micrometers. A backing of such thickness easily rips and tears, and can crease and pucker easily. Web-originated discs have a tendency to curl or cup with age if not stored under ideal humidity conditions. Unfortunately, if a thicker backing is used to attempt to eliminate the thin backing, cutting or punching the discs becomes difficult because of the thicker backing. In addition, thicker and tougher backings create more dulling of the cutting blades.
Abrasive discs that are produced by coating the preformed backing are usually singularly coated via a knife coater or graveure rolls, or sometimes even manually with a paintbrush. Unfortunately, as the coating meets the leading edge of the circular backing, the coating means may jump a bit leaving an undesirable high lip of the coating material on the edge of the disc. This lip is a high point on the abrasive disc which can cause undesirable scratches and gouges in the workpiece being abraded by the disc. A means of avoiding having to coat the edge of the disc thereby preventing the lip from forming is to either mask off the edge area, or lower it so that it is not coated. Such a procedure is not desirable due to increased labor and production costs associated with maintaining a uniform thickness coating.
The present invention is a coated abrasive article having a patterned abrasive surface. The article comprises a disc-shaped thermoplastic substrate having a first side. A plurality of raised portions are positioned on the first side of the substrate with recessed areas defined between each raised portion. A first adhesive layer is applied to the raised portions. Furthermore, an abrasive material is deposited into the first adhesive layer thereby coating the raised portions of the binder material to form an abrasive coating with the recessed areas remaining substantially free of abrasive material deposit. These raised portions result in a substrate that has a reduced tendency to form a raised lip during the manufacture of the coated abrasive.